SUPERPAVE MIX DESIGN Superpave Mix Design

Superpave Gyratory Compaction and Mixture Requirements Section objectives Describe the Superpave gyratory compactor Review the Superpave mixture requirements Summarize the moisture sensitivity test Final Result Participant will know the principles of the SGC and what mix criteria are included in the Superpave system Superpave Mix Design

Goals of Compaction Method Simulate field densification traffic climate Accommodate large aggregates Measure of compactability Conducive to QC Superpave Mix Design

Superpave Gyratory Compactor ? Basis Texas equipment French operational characteristics 150 mm diameter Up to 37.5 mm nominal size Height recordation ? ? Superpave Mix Design

height control and data measurement acquisition panel reaction frame loading ram mold tilt bar rotating base Superpave Mix Design

ram pressure 600 kPa 1.25 degrees (external) 150 mm diameter mold 30 gyrations per minute 1.25 degrees (external) Superpave Mix Design

Common SGC Types Troxler Pine Brovold Interlaken Rainhart 4140 AFGC125X HM-293 GYR-001 144 4141 AFG1A Superpave Mix Design

Professor Training Course SGC Compaction Curve % Gmm The increase in density (%Gmm) with each gyration is used to graph this compaction curve. 10 100 1000 Log Gyrations Superpave Mix Design

Gyratory Compaction We will evaluate the density of the HMA at two points: Ninitial Ndesign These N’s represent numbers of gyrations. Superpave Mix Design

Current AASHTO Ndesign Table Professor Training Course Current AASHTO Ndesign Table Traffic Level N initial design 6 50 0.3 to < 3.0 7 75 3.0 to < 30.0 8 100 9 125 Compaction Level < 0.3 > 30.0 The SGC requirements vary with traffic levels. The higher the traffic levels the higher the values of Ninitial, Ndesign and Nmaximum. Some States use different Ndesign Tables Superpave Mix Design

Gyratory Compaction The density (Gmb) @ Ndesign is the most important. This is where we will calculate the volumetric properties. Ninitial and Ndesign are points at which we use to check the compactability and densification of the HMA. Superpave Mix Design

Four Steps for Superpave Mix Design 1. Materials Selection 2. Design Aggregate Structure TSR 3. Design Binder Content 4. Moisture Sensitivity Superpave Mix Design

Example Project Data- Project on I-43 Milwaukee, Wisconsin 18,000,000 ESAL Design Asphalt Overlay - 88 mm total thickness 38 mm - wearing course (12.5 mm NMAS) 50 mm - intermediate course (19 mm NMAS) Superpave Mix Design

4 Steps of Superpave Mix Design 1. Materials Selection 2. Design Aggregate Structure TSR 3. Design Binder Content 4. Moisture Sensitivity Superpave Mix Design

Step 1. Materials Selection Binder Selection Binder grade is specified in nearly all cases Selecting the supplier of the binder is most often based on cost. Aggregates Selection Choice of aggregates is usually limited to locally available materials Superpave Mix Design

Project Weather Conditions Professor Training Course Project Weather Conditions 52 55 -32 -26 -40 -30 -20 -10 10 20 30 40 50 60 70 Pavement Temperature (°C), Milwaukee, Wisc. Superpave Mix Design

Climate Based Selection PG 58-34 PG 52-28 Asphalt Binder Grades Milwaukee, Wisc. Climate Based Selection -40 -30 -20 -10 10 20 30 40 50 60 70 Pavement Temperature (°C), Milwaukee, Wisc Superpave Mix Design

Binder Selection Milwaukee, Wisc PG 52-28 PG 58-34 Reliability(%) 50 74.5 99.9 99.6 Selected PG 58-34 Superpave Mix Design

Temp-Vis Relationship PG 58-34 Binder 5 Mix Temp Range: 165-172°C Comp Temp Range: 151-157°C 1 Viscosity, Pa-s Compaction Range Mixing Range 0.1 0.05 100 110 120 130 140 150 160 170 180 190 200 Temperature, C Superpave Mix Design

Select Aggregates Available Stockpiles #1 stone 12.5 mm chip Manufactured sand Screen sand Superpave Mix Design

Aggregate Properties Superpave Mix Design

Coarse Aggregate Angularity Test Results Aggr. 1+ Frac Faces Crit. 2+ Frac Faces Crit. #1 Stone 92% 88% 12.5 mm Chip 97% 95% min 94% 90% min 9.5 mm Chip 99% 95% Superpave Mix Design

Fine Aggregate Angularity Test Results Aggregate % Air Voids Criterion Manufactured Sand 52% 45% min Screen Sand 40% Superpave Mix Design

Flat & Elongated Particles Test Results Aggregate %Flat & Elongated Criterion #1 Stone 0% 12.5mm Chip 0% 10% max. 9.5mm Chip 0% Superpave Mix Design

Sand Equivalent Test Results Aggregate Sand Equivalent Criterion Manufactured Sand 47 45 min Screen Sand 70 Superpave Mix Design

4 Steps of Superpave Mix Design 1. Materials Selection 2. Design Aggregate Structure TSR 3. Design Binder Content 4. Moisture Sensitivity Superpave Mix Design

Selection of Design Aggregate Structure Establish trial blends Check aggregate consensus properties Compact specimens Evaluate trial blends Select design aggregate structure Superpave Mix Design

Gradation Percent Passing 100 max density line nom max size max size control point .075 .3 2.36 4.75 9.5 12.5 19.0 Sieve Size, mm (raised to 0.45 power) Superpave Mix Design

IH-43 Trial Gradations % PASSING 19.0 mm Nominal Mixture 100.0 90.0 80.0 70.0 Trial Blend 3 Trial Blend 1 60.0 % PASSING 50.0 40.0 Trial Blend 2 30.0 20.0 10.0 0.0 0.075 2.36 19.0 Sieve Size (mm) raised to 0.45 power Superpave Mix Design

Example Trial Blends Trail Blend 1 Trial Blend 2 Trial Blend 3 #1 Stone 25 30 10 ½” Chip 15 3/8” Chip 22 13 Mfg Sand 18 17 31 Scr. Sand 20 14 Superpave Mix Design

Aggregate Consensus Properties Blended aggregate properties are determined Property Criteria Blend 1 Blend 2 Blend 3 Coarse Ang. 95%/90% min. 96%/92% 95%/92% 97%/93% Fine Ang. 45% min. 46% 46% 48% Flat/Elongated 10% max. 0% 0% 0% Sand Equiv. 45 min. 59 58 54 Combined Gsb n/a 2.699 2.697 2.701 Combined Gsa n/a 2.768 2.769 2.767 Superpave Mix Design

Compact Specimens (Trial Blends) Establish trial asphalt binder content Establish trial aggregate weight Batch, mix, and compact specimens Determine Nini and Ndes Determine mixture properties Superpave Mix Design

Professor Training Course Specimen Preparation Specimen height Mix design - 115 mm (4700 g) Moisture sensitivity - 95 mm (3500 g) Loose specimen for Gmm (Rice) Sample size varies with NMAS 19 mm (2000 g) 12.5 mm (1500 g) 150 mm Superpave Mix Design

Batching Samples of Trial Blends Superpave Mix Design

Superpave Mix Design

Short Term Aging Two hours at the compaction temperature Superpave Mix Design

Superpave Mix Design

Superpave Mix Design

Superpave Mix Design

Measure Gmb, Gmm and calculate volumetric properties Superpave Mix Design

Superpave Mixture Requirements Professor Training Course Superpave Mixture Requirements Specimen height Mixture volumetrics Air voids Voids in the mineral aggregate (VMA) Voids filled with asphalt (VFA) Dust proportion %Gmm @ Nini Superpave Mix Design

Trial Blend Results Property 1 2 3 Trial Binder Content 4.4% 4.4% 4.4% %Gmm @ Ndes 96.2% 95.7% 95.2% %Gmm @ Nini 87.1% 85.6% 86.3% %Air Voids 3.8% 4.3% 4.8% %VMA 12.7% 13.0% 13.5% %VFA 68.5% 69.2% 70.1% Dust Proportion 0.9 0.8 0.9 Superpave Mix Design

Estimated Volumetric at 4% AV Pbe = Pbi – 0.4 x (4-Va) Pbe: estimated design asphalt content Pbi: asphalt content used in trial blends VMAe = VMAi + C x (4-Va) VMAe: estimated VMA at design asphalt content VMAi: initial VMA of trial blend C= constant: 0.1 when air voids < 4% and 0.2 when air voids > 4% Superpave Mix Design

Volumetric Design Criteria Superpave Mix Design

Compare Trial Blends to Mixture Criteria Blend 1 2 3 Criteria Binder Content 4.3% 4.5% 4.7% %Gmm @ Nini 86.9% 85.9% 87.1% < 89% %Air Voids 4.0% 4.0% 4.0% 4.0% %VMA 12.7% 13.0% 13.3%  13.0% %VFA 68.5% 69.2% 70.1% 65-75% Dust Proportion 0.9 0.8 0.9 0.6-1.2 Superpave Mix Design

Select Design Aggregate Structure What to do if none of the 3 trial blends are acceptable? Recombine aggregates to form further trial blends (i.e., Blend 4, Blend 5, etc.) Obtain new materials (aggregates, asphalt binder, modifiers) Superpave Mix Design

4 Steps of Superpave Mix Design 1. Materials Selection 2. Design Aggregate Structure TSR 3. Design Binder Content 4. Moisture Sensitivity Superpave Mix Design

Determining the Design Asphalt Content The selected trial blend becomes the design aggregate structure. Batch, mix, and compact more samples with this gradation with four asphalt contents. Determine volumetric properties Select Pb at 4.0% air voids and check other volumetric properties. Superpave Mix Design

Superpave Mix Design

Design Binder Content Samples %Gmm @ Nini 85.7% 87.1% 87.4% 88.6% %Gmm @ Ndes 94.6% 96.1% 97.1% 98.2% %Air Voids 5.4% 3.9% 2.9% 1.8% %VMA 13.3% 13.1% 13.3% 13.5% %VFA 59.4% 70.2% 78.2% 86.7% Dust Proportion 1.0 0.9 0.8 0.7 Superpave Mix Design

Densification Curves I-43, 19.0 mm NMAS, Blend 3 98.0 96.0 % MAX THEORETICAL DENSITY 89.0 4.2% AC 85.0 4.7% AC 5.2% AC 80.0 5.7% AC 75.0 1 10 100 1000 NUMBER OF GYRATIONS Superpave Mix Design

Professor Training Course air voids Mix Air Voids Requirement % binder 4% at Ndes Regardless of the Traffic Level Regardless of the traffic levels the Air voids requirement is 4%. Superpave Mix Design

Air Voids - Example Mix Design I-43 Binder Course, Blend 3 8.0 6.0 Air Voids = 4% 4.0 2.0 0.0 3.7 4.2 4.7 5.2 5.7 6.2 % ASPHALT BINDER Superpave Mix Design

Mix VMA Requirements Voids in the Mineral Aggregate % binder NMAS, mm Minimum VMA, % 9.5 15.0 12.5 14.0 19.0 13.0 25.0 12.0 37.5 11.0 Superpave Mix Design

VMA – Example Mix Design I-43 Binder Course, Blend 3 14.5 13.5 VMA = 13.2% 12.5 3.7 4.2 4.7 5.2 5.7 6.2 % ASPHALT BINDER Superpave Mix Design

Mix VFA Requirements Voids Filled with Asphalt % binder Traffic 106 ESALs Range of VFA, % < 0.3 70 - 80 < 1 65 - 78 < 3 65 - 75 > 3 65 - 75 Superpave Mix Design

VFA – Example Mix Design I-43 Binder Course, Blend 3 100.0 90.0 80.0 VFA = 70% 70.0 60.0 50.0 3.7 4.2 4.7 5.2 5.7 6.2 % ASPHALT BINDER Superpave Mix Design

Mix Requirement for Dust Proportion 100 92 83 65 48 36 22 15 9 4 Mix Requirement for Dust Proportion % weight of - 0.075 material % weight of effective asphalt 0.6 < < 1.2 Unabsorbed binder in mix Superpave Mix Design

Dust Proportion – Example Mix Design I-43 Binder Course, Blend 3 1.8 1.2 DP = 0.9 0.6 3.7 4.2 4.7 5.2 5.7 6.2 % ASPHALT BINDER Superpave Mix Design

%Gmm @ Nini %Gmm @ Nini = 87.1% I-43 Binder Course, Blend 3 90.0 88.0 86.0 84.0 82.0 80.0 3.7 4.2 4.7 5.2 5.7 6.2 % ASPHALT BINDER Superpave Mix Design

Select Design Asphalt Binder Content Summary of Mixture Properties @ 4.7% AC Property Result Criteria %Air Voids 4.0% 4.0% %VMA 13.2% >13.0% %VFA 70% 65-75% D/A Ratio 0.9 0.6-1.2 %Gmm @ Nini 87.1% <89% Superpave Mix Design

4 Steps of Superpave Mix Design 1. Materials Selection 2. Design Aggregate Structure TSR 3. Design Binder Content 4. Moisture Sensitivity Superpave Mix Design

Moisture Sensitivity AASHTO T 283 Measured on proposed aggregate blend and asphalt content Tensile Strength Ratio 80 % minimum 3 Conditioned Specimens 3 Dry Specimens Superpave Mix Design

AASHTO T 283 Conditioning Short term aging Loose mix 16 hrs @ 60°C Comp mix 72-96 hrs @ 25°C Two subsets with equal voids One “dry” One saturated Dry 6 to 8 % air 6 to 8 % air 55 to 80 % saturation Superpave Mix Design

AASHTO T 283 Conditioning Optional freeze cycle Hot water soak 16 hours @ -18 oC Optional freeze cycle Hot water soak 24 hours @ 60 oC Superpave Mix Design

AASHTO T 283 Test Procedure 51 mm / min @ 25 oC Avg Dry Tensile Strength Avg Wet Tensile Strength TSR =  80 % Wet Dry Superpave Mix Design

Calculate %TSR Wet Strength %TSR = 100* Dry Strength 721 kPa = 100* = 82.6% 872 kPa Criterion is 80% minimum. Design asphalt mixture exceeds the minimum requirement. Superpave Mix Design

Design Asphalt Mixture Aggregate Gradation: 25 mm 100% 19.0 mm 97% 12.5 mm 89% 9.5 mm 77% 4.75 mm 44% 2.36 mm 32% 1.18 mm 22% 0.6 mm 15% 0.3 mm 8% 0.15 mm 4% 0.075 mm 3.5% Aggregate: 10% #1 Stone 15% 12.5mm Chip 30% 9.5mm Chip 31% Manuf. Sand 14% Screen Sand Asphalt Binder: 4.7% PG 58-34 Superpave Mix Design

Questions – does it all make sense? Superpave Mix Design